April 5, 2022

How will 5G DAS and 4G/LTE DAS implementations differ?


Interview with William Wong – DAS Engineering Manager at ADRF

How should decision-makers prepare for 5G DAS deployments? Where should mmWave and C-band be deployed? What do you expect to see on the carrier front with 5G? What components are needed?

What are the frequency bands associated with 5G?

5G technology is carried over low, mid, and high-frequency bands with their own characteristics that alter how distributed antenna systems must be architected within buildings. High bands, such as mmWave, provide the fastest speeds and lowest latency but cover shorter distances and are easily disrupted by man-made and natural obstacles. Conversely, low bands like 600MHz offer slower 5G speeds but can travel longer distances and are more resilient to interference by materials. Mid band frequencies 2.5GHz and C-band are middling in both coverage and speeds. 

For the purposes of this discussion, the two primary 5G frequency bands we expect to see moving forward are mmWave and C-band. Each brings different strengths to a 5G deployment, helping to create tailored signals for specific use cases. mmWave has the highest bandwidth of available technology, while C-band is a newer trend in the wireless industry. During a recent auction, all major carriers bid heavily on C-band and spent over $80 billion.

What’s different about mmWave?

mmWave provides higher bandwidth than C-band, allowing for better download and browsing speeds, as well as lower latency. The caveat is that it does not travel as far as other bands as it requires a line of sight to the antenna. With this smaller coverage area, mmWave DAS needs more antennas in a space than a 4G/LTE system would require.

This is the same trend we saw when we jumped from 3G to 4G/LTE frequencies. Repeater placement can also help overcome any problem areas, like stairwells, where coverage propagation is a challenge.

What’s C-band’s role?

C-band has a higher frequency than bands used for 4G/LTE technology, but has higher antenna sensitivity, meaning it doesn’t propagate as well. When compared to 4G/LTE, C-band is better for wider deployment, but increased antenna sensitivity requires a denser antenna deployment within the DAS. It doesn’t require as much as mmWave, but it’s an increase from the previous generation. C-band can go through walls and its DAS is implemented in the same way as 4G/LTE bands.

How should decision-makers prepare for 5G DAS deployments?

The best thing you can do is work with your original equipment manufacturer (OEM) to have a clear understanding of the available products, and make sure the system is designed to adequately provide coverage based on the building or venue’s shape , size, and building materials.

As with any emerging technology, a strong partnership between the manufacturer and customer in the initial stages will help fine-tune applications.  System integrators also map the network on radio planning software, such as Ranplan and IBWave, to see how the current RF environment impacts the necessary antennas, sectors, and positioning of the DAS.  This helps them avoid unwanted costly surprises mid-deployment.

Where should mmWave and C-band be deployed?

When looking at deploying 5G in a building or venue, it’s important to understand how the individual areas within the entire space are used.  For example, mmWave offers faster browsing and download speeds but doesn’t propagate the signal as well as C-Band.  This makes mmWave better suited for high-traffic but confined areas, like a hotel lobby or large meeting space, and C-band better for hallways or other less densely-populated areas.

Think of mmWave 5G as a hot-spot of innovation for specific use cases where the combination of mid-band and low band can more closely resemble a traditional nationwide network.

What do you expect to see on the carrier front with 5G?

5G allows really high channel bandwidth, about 100 MHz, which helps to improve speeds and data capacity for the end-user.  It also has wider channels when it comes to the various mobile carriers and we’re seeing differences in the 5G deployment strategy.  Some will use both mmWave and C-band, others are looking into the BRS spectrum, which includes 2496-2690 MHz.

What components are needed?

When planning for your 5G DAS deployment, expect that all passive components including splitters, couplers, and antennas will need to support the desired frequency band.

The design and deployment process with 5G DAS is similar to how it’s currently done with 4G/LTE.  The bands are more sensitive and require denser antenna placement, but the overall systems will remain similar.  There are modular products available that can upgrade equipment to C-band using an overt line.  Overall, 5G deployments should not require a complete overhaul of the existing system.